Typically in communication systems, assigned channels are employed for sending data and also for control signaling or messaging of the system. Control signals or messages may be transmitted in control channels (CCHs) and are used for both the forward link transmissions, also known as the downlink transmission, from a network or base station to user equipment, and reverse link transmission, also known as uplink transmissions, from the user equipment to the network or base station. Here control signaling refers to reference signal or pilot, or synchronization signal transmissions (etc.) while control messaging refers to transmission of system information (including network and user equipment configuration information), scheduling and resource assignment information, Hybrid ARQ information (redundancy version information, new data indicator, Hybrid ARQ process ID information), power control information, paging information, random access response information, etc. In systems, such as Long Term Evolution (LTE) of UTRA, where the downlink control channel is composed of a single decodable element (called Control Channel Element (CCE)), or an aggregation of decodable elements (called Control Channel Elements (CCEs)), a user equipment must identify from a large group of CCEs the subset of CCEs intended for the particular user equipment. The subset of CCEs intended for a particular user equipment to monitor or attempt to decode at a particular CCE aggregation level, L, (e.g., L=1, 2, 4 or 8 CCEs) is called the set of resources for that user equipment at the particular CCE aggregation level, L. The set of resources for a user equipment contains one or more resource subsets where each resource subset comprises one or more CCEs corresponding to the aggregation level and the resource subset corresponds to a candidate downlink control channel also called a physical downlink control channel (PDCCH) candidate. A user equipment attempts to decode on each resource subset all of the PDCCH types assigned to it to monitor in the control region. There is one blind decoding on a resource subset for each control channel message type with distinct size the user equipment is assigned to monitor. Control channel types with distinct size in terms of the number of bits that make up the control channel payload (including the CRC) also have a distinct coding rate. In one example, convolutional coding is used to code the control channel information making up the control channel for each type. In LTE the PDCCH type is referred to as a Downlink Control Information (DCI) format type. The number of control channel types assigned to a user equipment to monitor is dependent on the transmission mode (e.g. downlink MIMO or downlink single antenna) assigned to the user equipment via higher layer signaling such as RRC (Radio Resource Control) signaling. The set of resources or resource subsets or PDCCH candidates the user equipment needs to monitor at an aggregation level, L, is defined in terms of a search space at that aggregation level, L. There is one search space for each aggregation level where the aggregation levels are L=1, 2, 4, and 8 and contain PDCCH candidates (resource subsets) each composed of L contiguous and consecutive CCEs. A user equipment thus has one set of resources in each search space. This means all of the PDCCH DCI format types assigned to a user equipment to monitor all have the same CCE locations in the set of resources in a search space. Each downlink control channel message type with distinct size and hence distinct coding rate assigned to a user equipment for monitoring must be separately blind decoded. That is, the more control channels with different coding rates assigned to a user equipment the more blind decodings it must perform when searching for the downlink control messages in the control region of each subframe.
When the user equipment checks the CCH candidate set to obtain the control information, if present, it has no knowledge which control channel in the CCH candidate set is used. Thus, the user equipment performs blind detection on all the control channel candidates in the control channel candidate resource set. The flexibility provided by blind detection has the advantage of reducing the overall amount of channel resources needed for control. Such flexibility allows each grant size to adapt to the necessary number of resources for the grant to be reliably received, rather than always using the worst case grant size. For example, for very good channel quality, a single CCE might be used with high confidence that the user equipment will reliably receive the control signal, whereas for very poor signal quality, such as where the user equipment is near the edge of a cell, a large number of CCEs might be used. Thus, blind decoding allows the base station to dynamically select the control channel aggregation size such that a large number of CCEs need not be used all of the time.
On the other hand, increasing the number of blind decodings per subframe control region requires higher complexity in the user equipment. A large number of blind decodings is not desirable, because it may produce excessive hardware complexity to complete all the blind decodings per each subframe control region. It may also elevate the false detection probability given the size limits of error correction code. It may further negatively impact power consumption in the user equipment. A large number of blind decodings may occur from the support of a large number of downlink control channel message types such as which may occur with carrier aggregation (assigning resources on multiple carriers or component carriers), support of enhanced transmission schemes (e.g., frequency-contiguous and frequency-non-contiguous resource allocation, MIMO with different number of layers, CoMP (Coordinated Multiple Point Transmission)), etc. Thus, there is a need for a method for reducing the number of blind decodings and complexity in the user equipment.